FIG. 1 is the structural figure of a conventional fuel cell system, comprising a fuel flow layer 27, a first power/signal transmission layer 19, an anode current collection layer 13, a membrane electrode assembly (MEA) layer 11, a cathode current collection layer 15, a second power/signal transmission layer 23 and an electromechanical control layer 21, wherein the anode current collection layer 13, MEA layer 11 and cathode current collection layer 15 construct a fuel cell core component 30. Taking the direct methanol fuel cell system as an example, fuel flow layer 27 flows through methanol solution and proceeds anode electro-chemical reaction on the anode terminal of MEA layer 11, the reaction formula is:CH3OH+H2O→6H++6e−+CO2The cathode electro-chemical reaction on the cathode terminal is formulated as:1.5O2+6H++6e−→3H2OAccordingly, the chemical energy is directly converted into low-voltage DC electrical power and delivered to the load 20.
In a direct methanol fuel cell system, when the used anode fuel of methanol solution is exhaust, one has to cease the electro-chemical reaction in the direct methanol fuel cell system to prevent the damage of fuel cell core component 30 which results in irreversible damage. Also another one has to supply methanol solution to the direct methanol fuel cell system for the demand of electro-chemical reaction. In order to avoid permanent damage, the first power/signal transmission layer 19 is placed a liquid level measurement system to detect the liquid level of anode fuel in the methanol solution.
The conventional liquid level measurement systems include capacitive, buoy, pressure, photo-sensitive, and acoustic measurements. These liquid level measurement systems always have volume and space constraints in practice, and also need huge and complicated mechanics and circuitries to measure the liquid level variation and thus limit many liquid level measurement systems in usage. Furthermore, in the small or miniaturized direct methanol fuel cell system, the conventional liquid level measurement system utilized in such small space always fails to effectively measure the liquid level variation, and even fails to use it. Therefore, the conventional liquid level measurement system design still has many shortages in the fuel cell system and needs to be improved.